Effect Of Urine Volume On Apparent Urine Nitrogen Accumulation By A Pasture Sward#

Abstract

Management intensive grazing (MIG) has the potential to increase dairy farm profitability in the northeast United States, but recent lysimeter studies in this region have shown that a substantial amount of NO3-N applied in cattle urine is leached below the root zone. Projecting the results of these lysimeter studies over a pastured landscape indicates that water quality standards may not be achieved, even at normal stocking rates. However, these projections were made from data based on a single volume of urine application. How the urine volume (i.e., size of cow) affects NO3-N accumulation by pasture herbage and how this accumulation subsequently affects the amount of NO3-N that is leached from a urine deposition in the climatic conditions of the northeast U.S. is not known. A two growing season field study was conducted to determine the impact area from synthetic urine applied in 1, 2, and 3 L volumes to a predominantly orchardgrass (Dactyls glomerata L., cv. ‘Pennlate’) sward. Dry matter yields and apparent urine N accumulation (AUNA) data indicated that urine N affected plant growth out to 50 cm from the point of deposition. However, percent apparent urine nitrogen (N) accumulation (PAUNA) out to 50 cm was similar to PAUNA in the previously reported work in which urine N was applied to 60 cm diameter (30 cm radius) drainage lysimeters. Therefore, we conclude that restriction of urine application to a 60 cm diameter lysimeter does not appreciably affect the amount of residual urine N in the soil that would be subject to leaching. #Mention of a brand name does not imply a recommendation by USDA.